Automatic switch



June 19, 1928. 1,674,489

H. W. VICKERY AUTOMATIC SWITCH Filed Nov. 28, 1924 Fig. L

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Patented June 19, 1928.

UNITED STATES PATENT OFFICE.

HARRY W. VICKEBY, OF LYNN, MASSACHUSETTS, ASSIGNOR T GENEBLAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

AUTOMATIC SWITCH.

Application filed November 28, 1924. serial No. 752,529.

My invention relates to electric switches and in particular to an automatic two-way fluid contact switch. In certain localities where electric lights are used, it is prescribed by law that theatre exits shall be provided with emergency lighting facilities in order that a proper illumination of the exits shall be maintained in the event that the regular source of electric suppl fails.

An auxiliary source of electric supply such as a stora e battery may be provided to which the lights may be connected whenever the regular source fails. As soon as the regular source is again established, the lights should be promptly switched back to the regular system in order to preserve the storage battery. It is required that the switching operation be controlled automatically in response-to a failure in the regular source of supply. Y

My invention relates to a simple, rugged, reliable switch, particularly designed for performing the functions above mefitioned although the switch is by no means limited to such use.

In carrying my invention into effect, I refer to provide a pair of enclosed cham ers containing a suitable gas and connected together by a capillary connection in which is entrapped a quantity of conducting fluid such as mercury forming a circuit terminal. Each chamber contains another circuit terminal arranged to alternately connect with the terminal formed by the conducting li uid in the communicating tube. An electric eater is provided for one chamber and is permanently connected across the regular source of supply so that when this heater is enerized, the fluid in the capillary tube will be orced toward the other chamber to connect with the terminal therein. When the regular source of supply fails, the gas in the heater chamber quickly contracts and the readjustment of the gas pressure forces the conducting liquid to break connection in the other chamber and make connection in the chamber provided with the heater.

The features of my invention which are believed to be novel and patentable will be ointed out in the claims appended hereto.

or a better understanding of my invention, reference is made in the following description to'the accompanying drawing in which Fig. 1 shows a preferred embodiment of my invention and its circuit connections as used for an emergency lighting installation; and Fig. 2 represents a different operating condition of the switch shown in Fig. 1.

Referring now to Fig. 1 10 and 11 re resents two parts of a sealed container ma e of some such material as glass. 10 may be called the heating chamber and 11 the expansion chamber. These chambers are connected together at their lower. ends by the U-shaped tube 12 and each chamber contains cup portions 13 and 14 at their lower extremities separated from the U-shaped communicating tube 12 by low dams 15 and 16 formed in the bottom walls of the chambers. The cups and the U tube contain sufiicient conducting fluid 17 such as mercury to overflow one or the other of the dams, the condition of the fluid depending upon the relative gas pressures in the twochambers. The cups and the lower extremities of the U tube contain electric terminals 18, 19 and 20 sealed in the glass walls to connect the conducting fluid to external circuits. The heating chamber 10 contains an electric heater 21 above the level of the fluid which is connected by sealed-in terminals 22 to the exterior of the chamber.

In the installation represented, the heater filament is connected to a regular source of supply represented at 23 and when voltage exists on this circuit, the heater is energized and heats the gas contained in chamber 10, thereby forcing the conducting fluid to the condition represented in Fig. 1 with dam 15 uncovered and dam 16 covered. The terminal 20 of the expansion chamber is connected to one side of source 23 by a connection 24. The other side of source 23 is connected to one side of a load 25, represented as lights, by a connection 26. The terminal 19 of the central U tube is connected to the other side of the load 25. It will thus be seen that so long as voltage exists across source 23, this source will be connected to the load 25 by reason of the fluid contact 100 circuit between terminals 19 and 20 above the dam 16. A second source of supply 27 represented as a storage battery, is connected between the line 26 to the load and the ter minal 18 of the heating chamber. Now, 105 should the source 23 fail, filament 21 will be deenergizecl and the gas in chamber 1') will quickl cool allowing the fluid conductor to reatliust its condition to that represented in Fig. 2 where it will be noted that 110 vessel 10 and is of suc the dam 16 is uncovered and dam 15 is covered. This disconnects the load 25 from source 23 and connects it to the storage battery 27 through terminals 18 and 19 and the fluid conductor between them. As soon as the voltage again comes on source 23, the filament 21 will be ener ed and the connections represented in' 1g. 1 reestablished. The amount of fluid conductor in the chambers 10 and 11 is preferably such that the circuit is broken at one dam just before it is made at the other. The dams may be of suflicient width to break a considerable current amperage without destructive heating of the ,glass. As represented in the drawings, the dam 16 in the expansion chamber has a slightly higher level than that of the heating chamber. With such an arran ment the. ses in the two chambers should be of sucg volume as to make the fluid level'about equal when the heater 21 is deenergized as represented in Fig. 2, leaving the hlgher dam uncovered and the lower dam covered. It is not essential, however, that'the dams have the relative heights represented, since other relations can readily be compensated for by a readustment of the gas pressure in the two chambers. For the best economy the two dams'should be'nearly the same level. The relative as pressures in the two chambers may readl y be altered by ti ping the device one way or the other and t en allowing the mercury toflow back in the tube 12 and the relative levels of the two dams can be altered by a slight tipping of the device in the proper direction. The heater 21 is preferab placed inside of the resistance as to take a ver small current and to be quickly heate to incandescence and thus operates as a visible signal to indicate the condition of the switch. The two chambers, being equally exposed to the surrounding air, are equally affected by changes in ambient temperature and the operation of the switch is therefore independent of such temperature changes. Suchan automatic switch is quiet, economical and reliable in its operation and is quickly responsive to the failure and the reestablishment of the voltage on source 23. It is simple and rugged in construction, re-

uires no attention and is equally suitable or direct or alternating currents on either source. It has no ex osed contacts or coils and consequently is ighly desirable from the standpoint of fire safety.

In accordance withthe provisions of the patent statutes, I havedescribed the prin- I cipleof operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire tohave it understood that .the apparatus shown and described is only illustrative and that the invention may be carried out by other arrangements.

What I claim as new and desire to secure by Letters Patent of the United States 1s:

1. A two-way switch comprising a heating chamber and an expansion chamber contain ing a heat expansible gas, said chambers being connected together by a tube in which there is entrapped a quantity of conducting fluid, fluid contacts in each chamber separated from the tube by low dams and an electric heater in one chamber adapted to cause the fluid in said tube to alternately overflow said dams when said heater is energized and deenergized respectively due to the variation in gas pressure under said conditions. I

2. A two-way switch comprising a pair of sealed containers connected together by a u-shaped tube, depressions in said containers" separated from said tube by low dams, a quantity of conducting fluid in said depressions and tube just suflicient to cause the fluid to overflow one dam only, a heat expansible gas contained in said chambers and separated by the conducting fluid in said tube, an electric heater contained in one of said chambers for operatin the switch, said heaterv being adapted to he heated to incandescence when ener ized and thereby serve as an indication of t e condition of the switch.

3. In a switching device, a sealed container comprising a heating chamber and a compression chamber, a U-shaped tube connectlng said chambers, a depression in the compression chamber separated from the tube entrance therein by allow dam, conducting fluid in saidtube and depression, external circuit'terminals sealed into said container to connect the fluid in said tube and depression to external circuits, an electric heater in the heating chamber and a heat expansible gas in said chambers, the relative pressures in the two chambers bein such as to cause the fluid to overflow sai dam when the heater is ener ized and to uncover said dam when the eater is deenergized.

In witness whereof, I have hereunto set my hand this 25th da of November, 1924.

HAR Y W. VYICKERY. 

